Description:

Objective:

The objective of this project was to develop heterogeneous acid-base catalysts to increase the economic and environmental performance of the traditional homogeneous catalysts used to make industrially important condensation products.

Summary/Accomplishments (Outputs/Outcomes):

The condensation/hydrogenation of acetone to methyl isobutyl ketone (MIBK)
was studied on a series of Ni- and Pd-supported oxide catalysts and a series of
Pd- and Pt-supported hydrotalcite (HTC) catalysts. The reaction experiments were
performed in a high-pressure reactor vessel equipped with a micro-Robinson
catalyst basket, in a semi-batch mode (liquid acetone, gaseous H2 reactant, and
N2 diluent) under moderate temperatures (100?150?C) and elevated pressures
(350?400 psig).

The synthesis of MIBK from acetone condensation has been demonstrated on
noble-metal-supported hydrotalcites (Pd/HTC and Pt/HTC). This process offers
significant advantages over the traditional three-step homogeneously catalyzed
acetone-to-MIBK process (Figure 1). It is environmentally benign because it does
not generate strongly basic wastewater streams. Finally, it is potentially
economically attractive because it eliminates the cost-intensive product
separation and waste disposal steps found in the traditional MIBK formation
process.

The results of this study indicate the complexity of maximizing the formation
of MIBK by the acetone condensation/hydrogenation on multifunctional catalytic
systems. The Pd/HTC and Pt/HTC catalysts showed up to 35 percent yield to MIBK
with minimal byproduct formation (mainly IPA). The highest MIBK yield was
obtained on the 0.1 percent Pd/HTC catalyst, indicating that minimal
hydrogenation activity was required for the MO-to-MIBK reaction. Pd was more
selective to MIBK than Pt at every loading, despite similar acetone conversions
for Pd/HTC and Pt/HTC catalysts. Acetone conversion was directly related to the
acidity/basicity of the catalyst, which were properties of the support rather
than the metal. Higher hydrogenation activity (higher metal loading, Pt instead
of Pd) resulted in greater selectivity to IPA.

The yield and selectivity of MIBK showed a maximum with reaction temperature
on a 0.1 percent Pd/HTC catalyst. Increasing the reaction temperature from 99?C
to 153?C resulted in enhanced acetone conversion, but it also tended to shift
product selectivity towards undesirable over-condensation products (mainly C9
cyclic species), thus severely limiting the yield of MIBK. The catalysts
studied have both condensation and hydrogenation activity. The relative rates of
these two reactions changed with reaction temperature, with a temperature
increase strongly favoring condensation over hydrogenation. Consequently, the
yield of MIBK would be expected to show a maximum with reaction temperature on
any multifunctional acetone condensation catalyst, but the position of this
maximum would be determined by the balance between the acidic/basic and hydrogenation properties of a particular catalyst.

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.